Disclosed herein are hot melt or phase change inks and methods for the use thereof. One embodiment is directed to a hot melt or phase change ink comprising a phase change ink carrier and a colorant comprising carbon allotrope colorants, in embodiments fullerenes, and in further embodiments, carbon nanotubes. Another embodiment is directed to an aqueous ink comprising an aqueous liquid vehicle and a colorant comprising a carbon allotrope. Another embodiment is directed to a method which comprises (a) incorporating into an ink jet printing apparatus a phase change ink comprising a phase change ink carrier and a colorant comprising a carbon allotrope colorant, in embodiments fullerenes, in further embodiments, carbon nanotubes; (b) melting the ink; (c) causing droplets of the melted ink to be ejected in an imagewise pattern onto the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, where the droplets quickly solidify to form a predetermined pattern of solidified ink drops.
In general, phase change inks (sometimes referred to as “hot melt inks”) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops. Phase change inks have also been used in other printing technologies, such as gravure printing. Phase change inks have also been used for applications such as postal marking, industrial marking, and labeling.
Phase change inks for color printing typically comprise a phase change ink carrier composition which is combined with a phase change ink compatible colorant. In a specific embodiment, a series of colored phase change inks can be formed by combining ink carrier compositions with compatible subtractive primary colorants. The subtractive primary colored phase change inks can comprise four component dyes, namely, cyan, magenta, yellow and black, although the inks are not limited to these four colors. These subtractive primary colored inks can be formed by using a single dye or a mixture of dyes. For example, magenta can be obtained by using a mixture of Solvent Red Dyes or a composite black can be obtained by mixing several dyes. U.S. Pat. No. 4,889,560, U.S. Pat. No. 4,889,761, and U.S. Pat. No. 5,372,852, the disclosures of each of which are totally incorporated herein by reference, teach that the subtractive primary colorants employed can comprise dyes from the classes of Color Index (C.I.) Solvent Dyes, Disperse Dyes, modified Acid and Direct Dyes, and Basic Dyes.
The colorants can also include pigments, as disclosed in, for example, U.S. Pat. No. 5,221,335, the disclosure of which is totally incorporated herein by reference.
Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and dot quality is improved.
Compositions suitable for use as phase change ink carrier compositions are known. Some representative examples of references disclosing such materials include U.S. Pat. No. 3,653,932, U.S. Pat. No. 4,390,369, U.S. Pat. No. 4,484,948, U.S. Pat. No. 4,684,956, U.S. Pat. No. 4,851,045, U.S. Pat. No. 4,889,560, U.S. Pat. No. 5,006,170, U.S. Pat. No. 5,151,120, U.S. Pat. No. 5,372,852, U.S. Pat. No. 5,496,879, European Patent Publication 0187352, European Patent Publication 0206286, German Patent Publication DE 4205636AL, German Patent Publication DE 4205713AL, and PCT Patent Application WO 94/04619, the disclosures of each of which are totally incorporated herein by reference. Suitable carrier materials can include paraffins, microcrystalline waxes, polyethylene waxes, ester waxes, fatty acids and other waxy materials, fatty amide containing materials, sulfonamide materials, resinous materials made from different natural sources (tall oil rosins and rosin esters, for example), and many synthetic resins, oligomers, polymers, and copolymers.
Aqueous inks generally comprise an aqueous liquid vehicle; a colorant; and optionally one or more additives. Examples of vehicles suitable for aqueous inks include water, glycols, mixtures of glycols, a mixture of water and a miscible organic component, such as a glycol, such as ethylene glycol, propylene glycol, diethylene glycols, glycerine, dipropylene glycol, polyethylene glycols, polypropylene glycols and the like, amides, ethers, carboxylic acids, esters, alcohols, organosulfides, organosulfoxides, sulfones, dimethylsulfoxide, sulfolane, alcohol derivatives, carbitol, butyl carbitol, cellosolve, ether derivatives, amino alcohols, ketones, and other water miscible materials, and mixtures thereof.
The use of dyes as colorants in solid or phase change ink compositions or aqueous inks results in brilliant colored images. However, certain soluble dyes can suffer from problems with thermal stability, light fastness, and dye migration. Further, custom syntheses required for certain dyes can make them expensive to produce. To overcome some of these issues, pigments can be selected as solid or phase change ink colorants or aqueous ink colorants. Pigmented inks have been successfully prepared and used in solid, phase change, and aqueous ink printers. Pigments can provide inherent robustness, thermal stability and light fastness. Pigments can also reduce or eliminate the problem of dye migration in printed images, whereby the mobility of a dye colorant within the wax based image can result in a distortion or smearing of the image over time. Further, pigments are less expensive than dyes therefore providing a significant manufacturing cost advantage. However, incorporating pigmented inks into ink jet inks can be technically challenging and pigmented inks can be subject to jetting difficulties.
While known compositions and processes are suitable for their intended purposes, a need remains for improved phase change and aqueous ink compositions. In addition, there is a need for aqueous and phase change inks that enable improved thermal stability of the inks manifested as the color's stability over time when heated in printers. There is also a need for aqueous and phase change inks that enable improved printer reliability. In addition, a need remains for aqueous and phase change inks that exhibit excellent hiding power such that paper fibers cannot be seen through a solid area image which results in diminished optical densities. Additionally, a need remains for aqueous and phase change inks having increased mechanical integrity. Further, a need remains for aqueous and phase change inks having improved mechanical integrity, such that printed images are resistant to physical abrasion, scratching, creasing and the like. Further, a need remains for a colorant capable of providing intense blackness for aqueous and phase change inks.
The appropriate components and process aspects of the each of the foregoing may be selected for the present disclosure in embodiments thereof.